Electronic circuit breakers make and break electrical connections to a load protected by the circuit breaker by causing a shunt trip, typically by energizing a solenoid that acts upon a trip mechanism for mechanically separating electrical contacts carrying electrical current from the line through the circuit breaker to the load. The solenoid requires a reliable source of power to ensure reliable tripping in response to the detection of certain electrical faults, such as ground faults. A power supply in the circuit breaker can be powered from the voltage on the line conductor(s) entering the circuit breaker. When the power supply is directly line-powered, it is susceptible to transients. As the voltage input to the power supply increases, the risk of damage caused by transients increases. For electronic circuit breakers that are rated for the high end of a low voltage (LV) range, such as between 120-600V, the energy in transients at a 600V input will be much higher. Because the sensitive electronics including signal processing circuits responsible for detecting a fault condition are powered by the power supply, they are exposed along the signal chain to any voltage transient appearing on the voltage input. Accordingly, a need exists for a transient suppression circuit for an electronic circuit breaker that can reliably absorb the energy in a high voltage transient. A need also exists for a noise suppression circuit that reduces noise caused by interference so that the fault-sensing electronics can operate reliably and consistently across the range of voltage input to the circuit breaker.
A need also exists for a power supply that can reliably energize the trip solenoid without using a high voltage component to cause the tripping event across a wide range of low voltage inputs to the power supply, such as between 120-600V, in electrical distribution systems. Aspects of the present disclosure are directed to fulfilling these and other needs.